Chem Final
liquid VS gas of alkanes
as we go up the table of hydrocarbons, boiling point gets lower and evaporate more easily and they are harder to condense (cool down first) (e.g. methane)
As the number of carbons goes up, boiling point (degrees C)
Increases
Refineries are exporting petcoke around the world, especially to energy-hungry _____, which got a fourth of all the fuel-grade petcoke the US shipped out.
India
Units of Energy
Joule (J), calorie (cal), British thermal unit (BTU)
The best fuel from an energy perspective is
Natural gas
Is the efficiency of an energy transformation process always less than 100% because the energy is destroyed?
No, energy cannot be destroyed. It simply changes forms (lost as heat mostly, sound, light)
Law of conservation of energy (1st law of thermodynamics)
energy is neither created or destroyed
calorie (cal)
amount of energy required to raise the temperature of 1 g of water by 1 degree Celcius
What type of coal has high energy content and low sulfur content, making it the most desirable fuel? (supply in US almost exhausted)
anthracite
What is the pattern in the number of C and H?
as we add a carbon, we add two hydrogens.
Bond energies
energy that must be absorbed in order to break a bond
A joule (J) is a unit of _______, a watt (W) is a unit of _____, and a Calorie (Cal) is a unit of _______.
energy; power; energy
All fuels combust, and reaction is always
exothermic
If more bond forming releases more energy than is used to break bonds, then overall reaction is
exothermic
Natural gas has caused many
explosions (oregon, bozeman, illinois, colorado)
Petcoke use to be used in industry, but those factories closed or moved. US refineries often do what with this un-used petcoke?
export it because they cannot sell it here (just want to get rid of it, so its cheap)
Total energy change (triangleE) =
final energy (products) - initial energy (reactants)
___________ bulbs generate light by sending an electrical discharge through an ionized gas
fluorescent
Energy can have many different ______ and can be _________ from one ____ to another
forms; converted; form
Crude oil is separated into its different useful _________ (components such as diesel and gasoline) at a refinery.
fractions
purpose of reforming
provide more branching (can raise the octane number of the molecule)
The % gasoline obtained from crude oil varies with ______ and with __________
region; processing
Advantages of Natural gas
relatively clean for a fossil fuel (few contaminants and burns completely so little sulfur, ash or soot emitted into atm), efficient: less GHG emitted per energy produced compared to coal. Easy to transport (pipelines across country) and use (pipelines into homes, instant energy) Safer in terms of spills, leaks ?
Benefits of coal
relatively easy to dig out of the ground and very cheap: about 1/16 cost of oil or natural gas per energy unit
Exothermic reaction
releases heat; products have lower energy than reactants; energy change has a negative sign
Coal is essentially a _______________ with and varies in
sedimentary rock; carbon content, moisture content, sulfur content, ash, trace metals (aluminum, mercury, copper, zinc, arsenic, lead)
As you go up the distillation tower, the molecules that condense out are
smaller molecules that have a lower boiling point temperature as well as condensation temperature
what types of oil are found as the distillation tower goes up (boiling point decreases)
starts with solids like asphalt, goes to fuel (liquid), and then refinery gases
Disadvantages of Natural gas
still a fossil fuel (so GHG emissions and nonrenewable) Needs processing can be dangerous to transport and store colorless/odorless/tasteless (unless treated)
"Clean coal" technology
technologies being developed to remove or reduce some pollutant emissions to the atmosphere.
Health and environmental advocates
the US is simply exporting an environmental problem because we dont want to deal with it
Fuels have different energy contents because
the difference in energy between reactants and combustion products varies (same combustion products always come out of all different fuels)
A calorimeter can be used to get the "heat of combustion" (energy content) of different fuels:
the heat given off when a specific substance is burned
30-70% of the "frack fluid" returns to
the surface (may have picked up salts and other species while underground)
With the use of a catalyst, the identity of products and reactants as well as the overall energy change are
unchanged
What is a Watt (W)?
unit of power (energy per time)
Compact fluorescent lamp (CFL)
use one-fifth to one-third the electric power of incandescents, and last ~10x longer. higher purchase price than incandescent, but can save over 5x its purchase price in electricity costs over its lifetime. contains mercury, which is toxic and complicates disposal.
Fracking
water mixed with a variety of compounds is forced deep underground into the non-permeable shale (1-3 miles deep) The high pressure water breaks up or "fracks" the shale, releasing the trapped gas or oil. Sand is added to the water as a proppant to keep the fractures in the shale open, thus enabling the oil/gas to flow to the surface
Phase transitions of water
water to ice is exothermic, water to water vapor is endothermic
Bonds can be both broken and formed at the same time; the overall heat change depends on
which bonds are broken and how many
Is the energy system at CU efficient?
yes; uses natural gas (70-75% efficient)
boiling of ethanol
endothermic
evaporation of gasoline
endothermic
activation energy
energy "hill" needed to initiate chemical reaction
Energy Efficiency of a Process
% efficiency = [energy produced in form you want ("useful energy") / total energy input] x 100
How does a coal burning power plant make electricity?
(1) coal is combusted (2) heat boils water in a closed, high-pressure system (3) steam turns a turbine to generate electricity
4 Disadvantages of Coal
(1) coal mining is dangerous (cave-ins, fires, explosions, poisonous gases) (2) environmental harm caused by coal mining (acid mine drainage, mountain-top mining) (3) dirty combustion products pollute air/water (soot, sulfur [acid rain], mercury, fly ash sludge (4) carbon dioxide emissions (has very high CO2 emissions per energy released-low efficiency PPs-, even "clean coal" processes do not typically address CO2)
How can you predict if a reaction will release heat (exothermic) or absorb heat (endothermic) ?
(1) if it is a combustion reaction it is exothermic (2) if heat (or energy) is written as a product or a reactant in a chemical equation (product = exothermic, reactant = endothermic) (3) from a reaction diagram with an energy axis (products lower in energy than reactants (exothermic) (4) if you are told the sign (+ / -) of the energy change of a reaction (energy difference negative = exothermic) (5) If you can calculate the heat change by knowing which bonds are broken and which bonds form
How to calculate overall energy change using bond energies
(1) write balanced reaction (2) draw lewis structures (3) figure out how many of each bond is broken or formed (4) energy change = bond energy (bonds broken) - bond energy (bonds formed)
1 W =
1 W = 1 J per second (J/s)
units of calories
1 cal; 1 kcal = 1 Cal (food)
How many calories (lower case!) and joules do you consume if you eat one Chunky Chocolate cookie with 110 Calories? (Conversions: 1 cal = 4.184 J, 1 kcal = 1 Cal = 1000 cal)
110,000 calories and 460,000 J
The average US household is reported to run at ____ W
1250
The heat of combustion of methane, CH4, is 50.1 kJ/g. How much heat would be generated if 2 mole of methane undergoes complete combustion? (you need the molar mass of methane)
1603 kJ
The Three Gorges Dam in China, the largest power station in terms of installed capacity (22,500 MW or 22.5 GW) (1 GW = 10^9 W). How many typical households could this provide energy for? (Household = 1250 W)
18 million
In 2016, the US sent more than 8 million metric tons of petcoke to India. __ times more than in 2010, and enough to fill the Empire State Building eight times
20
How many joules of electrical energy are produced if a 100 MW power plant runs at full capacity for 1 hour? (1 MW = 10^6 W, 1 W = 1 J/s)
3.6 x 10^11 J
The Valmont Power Plant natural gas turbine (43 MW) can generate 43 megajoules of energy per second. (1 MW = 10^6 W). How many households can it power? (household = 1250 W)
34,400 houses
Each day a power plant consumes coal that contains 1.3 x 10^13 J of chemical energy but generates only 5.0 x 10^12 J of electricity. How efficient is the power plant?
38.5 % efficient
A natural gas-fueled power plant is 36% efficient at turning the energy in natural gas into electrical energy. An amount of fuel containing 1.3 x 10^13 J of chemical energy is combusted. How much electrical energy can be produced from this amount of natural gas?
4.7 x 10^12 J
A power plant generates 40,000,000 J of electrical energy in 1 day. What is the average power output, in Watts, of this power plant? (W=J/s)
464 W
In a natural gas-burning power plant, 2.3 x 10^3 kg of natural gas (CH4) were combusted and 5.5 x 10^7 kj of electrical energy were produced. The energy content of CH4 is 50.1 kJ/g. how efficient (%) is the power plant at turning the chemical energy in natural gas into electrical energy?
48%
how many ways to predict if a reaction give off heat or absorbs it (and how much)
5
A light bulb emits 2.0 J of light energy. This type of light bulb is only 4% efficient at converting electrical energy into light. How much electrical energy is used?
50 J
A 60 W light bulb consumes __ J/s of energy of electrical energy
60
One train contains 125 tons of lignite coal and another car contains 70 tons of anthracite coal. Which amount of coal, if burned, could release the most energy? (E.C lignite = 16.2 kJ/g, E.C anthracite = 30.5 kJ/g) (1 ton = 9.07 x 10^5 g, 1 cal = 4.184 J)
70 tons anthracite
Estimated U.S Energy Use in 2012: ~95.1 Quads
A surprising amount of energy is "rejected", often as heat! (Heat you feel when you put your hand on a water heater, light bulb, warm exhaust from your car's tailpipe)
4 Advantages of Coal
Abundant and widespread, inexpensive (reliably so), safer/easier to transport than other fuels, comes out of the ground in usable form
Weekly article
Alberta oilsands waste exported by American refineries to pollution-choked India
A majority of the growth in coal use and power plants is from
Asia
From 1980-2010, what countries have increased coal consumption?
Asia, india, china (past few years)
Generic formula for alkanes
C(n: number of carbon) H(2n+2)
C12 alkane
C12H26
What is the overall efficiency of each kind of light bulb? How does this vary for CLFs?
CLFs require less energy and are more efficient (give off less heat)
Petcoke as fuel?
Can be used as fuel, but not typically in the US.
Oil sands exist in Russia, US, and Venezuela, but oil sands mining only occurs commercially in ______, which has 71% of worlds deposits
Canada (if only 30% of this oil was extracted, it could supply the entire needs of N. America for over 100 years)
Distillation Tower
Compounds are condensed at different heights and temperatures in tower. Smaller molecules need lower temperatures to condense, so they can travel further up the tower.
Major fractions retrieved from distillation
Crude oil goes through boiler into the distillation tower. The coker converts residual oil into smaller molecules via cracking but also yields "coke." Larger molecules are broken into smaller ones in the cracker. Atoms within a molecule are rearranged in the reformer.
A coal burning plant is fairly inefficient (e=33%). The plant needs to generate 1.0 x 10^12 J of electrical energy each day. How much coal (in g) must be combusted every day? (coal produces 30,000 J per g when combusted)
First find the energy of the coal that must be burned after the inefficiency is considered. Then find the mass of this coal. 1.0 x 10^8 g
Oil sands can produce ~20% more ____________ than conventional oil
GHG emissions
How can natural gas be released from the very deep, low-permeability gas-rich shale?
Hydraulic fracturing (fracking)
Calorimeter
If the reaction releases heat, the temperature of the water will increase. The exact temperature increase of the water tells you exactly how much heat was given off by the sample Can get energy content in kJ/g, cal/mole, etc.
Who produces oil? Who consumes oil? (Over time)
North America produces some, but not as much as the middle east. Even though the middle east in increasing its consumption, the majority of it is exported to consumers (europe, america, asia pacific [region increasing in consumption]. South/central America consumes a small amount.)
Cracking is done in order to form more economically viable molecules.
Often, long, heavy tar molecules are cracking into diesel and gasoline. Gasoline needs can't be met by the gasoline-sized molecules (C5-C12) that naturally occur in petroleum
What types of energy exist at each point in the generation of electricity from the combustion of coal?
Potential energy (fuel molecules) ---Burner---> Kinetic energy ---Turbine---> Mechanical energy ---Generator---> Electrical Energy
The petcoke burned in many factories and plants is contributing to filthy air in India, which already has many of the world's most polluted cities.
Tests on imported petcoke new New Delhi found it contained 17x more sulfur than the limit for coal, and 1,380 times more than for diesel (cheaper to buy). 1.1 million Indians die prematurely from air pollution every year, 50% of children have abnormal lung function
Which state has the most natural gas
Texas
How would you best define the efficiency of a light bulb
The percent of total electrical energy used that becomes light energy
Different forms of Energy
Thermal (heat), electrical energy, light, chemical energy, mechanical energy (motion)
How were fossil fuels formed?
They were once alive. FF were once prehistoric plants and animals (phytoplankton, zooplankton) that lived 100s of millions of years ago. Remains of organisms settled to the sea or lake bed and decomposed anaerobically (without O2). Over geological time, this organic matter was buried. High pressures and temperatures caused the formation of solid, liquid, and gaseous hydrocarbons (catagenesis).
What is the generation type of the local power plant, Valmont Generating Station
Unit 5 (offline) - steam turbine (coal) (184 MW) Unit 6 - combustion turbine (natural gas) (43 MW)
Are we going to run out of oil?
We are certainly running out of easy/cheap to extract oil.
Trends in Global Coal Use over time
When first introduced, America used a lot, but Asia quickly took over. Used in china, north america, europe, asia, india
Sulfur content vs Energy content: why is this relationship problematic?
You want sulfur to decrease as energy increases, but sulfur actually increases with energy content
How is the energy content of a fuel determined
a calorimeter
what is petroleum chemically speaking
a complex mixture of several hydrocarbon (CH) compounds
Why is the middle east responsible for the volatility in oil production?
a dip in production results in a dip in overall production
meting of ice
absorbs heat, endothermic
Endothermic reaction
absorbs heat; products have higher energy than reactants; energy change has positive sign
Many of the hydrocarbons in petroleum are called
alkanes
Kingston Fossil Plant (TN) coal fly ash slurry spill
ash sike ruptured at a solid waste containment area, releasing 1.1 billion gallons of coal fly ash slurry. the coal-fired power plant used ponds to "dewater" the fly ash sludge. The slurry covered 300 acres of surrounding land, damaging homes and glowing into nearby streams.
One fist-size lump of __________ coal contains 3,000,000 calories - enough energy to power a 75 watt bulb for two days.
bituminous
Refinery splits table of hydrocarbons based on
boiling point
Does it take energy to break a bond or form a bond?
breaking bonds requires energy (endothermic), forming bonds releases energy (exothermic)
fly ash sludge
byproduct of coal combustion
Petroleum Coke (Petcoke)
carbonaceous solid produced from refinery coker units
examples of catalysts
catalytic converter, catalytic cracking, catalytic O3 destruction
characteristics of petcoke
cheaper and burns hotter than coal, emits 30-80% more CO2 on a per mass basis, emits 5-10% more CO2 than coal on a per energy basis. Contains more sulfur than coal. EPA rejects permit applications to burn petcoke
four techniques that are being used in "clean coal":
chemically washing impurities from coal, gasification of coal into a fuel that will burn at lower temperatures (less NOx), scrubbing SO2 from emissions, "dewatering" lower rank coals to improve their energy content
GHG emissions for many methods of electricity generation
coal (esp. lignite, poorest quality) produce the most GHG per energy produced. There is CO2 emitted at other times in the energy generating process besides power plant emission (green bars). Renewables and nuclear produce trivial quantities of GHGs compared to the three fossil fuel types.
most of the modern industrial world we see around us was built with
coal power
three fossil fuel types
coal, oil (petroleum), natural gas
Chemistry of Coal
complex mixture of substances (approximated formula, ~85% carbon)
Energy is not destroyed; rather, it is _________ to a less desirable form
converted
US transportation demands require ~50% of crude oil be converted into gasoline; this requires
cracking
Energy
defined as the capacity to do work or transfer heat
Primary refining process is called
distillation - separates molecules based on their boiling point
CO2 emissions go ____ as power plant efficiency goes __.
down; up
Cogeneration (CHP "combined heat and power") is
dual-purpose and improves efficiency of power plant (uses "waste heat" for heating)
Advantages of petroleum
easily extracted (often) and transported (through pipelines), 40-60% more energy per gram than coal
Light bulbs can vary widely in their __________
efficiency
New coal technologies have improved __________ and less _________, but coal is still high compared to alternatives
efficiency; emissions
Natural gas provides provides
electricity (natural gas power plants), heat directly to a home (furnace)
If bond forming releases less energy than is used to break bonds, then overall reaction is
endothermic
How is each barrel of petroleum used? from highest to lowest
gasoline, diesel and home heating, other products, (plastics, pharmaceuticals, fabrics, asphalt for roads, tars for roofing, solvents for paints), jet fuel, heavy fuel oil, liquified refinery gas
Modern natural gas power is about ____ as CO2-intensive as the best coal power plants
half
condensation of liquid water
heat is released (leaves the system); exothermic
In an exothermic phase transition,
heat must be released
Canadian oil sands crude oil is
heavy crude - when refined and put through a coker unit, it produces a lot of petroleum coke
alkanes are
hydrocarbons (C + H) with only single bonds between carbons.long chains of carbons with h attached everywhere you have room for one. Different ways to write it
____________ bulbs emit light by heating the filament present in the bulb
incandescent
Oil sands require
intensive processing to produce usable crude - it can take two tons of oil sand to produce just one barrel of oil (also energy, water).
Same molecular formula but atoms connected differently
isomer
Light crude oil is more desirable than heavy crude oil because
it produces a higher yield of gasoline if untreated.
Divide ______ by _______ to get watts
joules; seconds
Cracking
large hydrocarbon molecules are broken into 2 or more smaller molecules (Can be thermal (high temps needed) or catalytic (uses catalyst, can be done at lower temps)
The efficiency of an energy transformation process is always ____ than 100%
less
How does a catalyst speed up a reaction?
lowers activation energy of the reaction (the "hill" that must be climbed), thus reaction is easier to get started and faster
oil sands (tar sands)
mixture of clay, sand, water, and bitumen, a heavy viscous oil. Can be mined and processed to extract the bitumen
isomers
molecules with same molecular formula but different structure (have sam properties) (when trying to determine, count ratio of molecules and compare)
The effect of adding oxygen in a fuel
more oxygenated fuel lowers energy content (smaller energy difference)
Joule (J)
most common unit of energy in science
Disadvantages of Petroleum
must be refined before use, east-to-obtain oil is limited, price is volatile
Petcoke as "environmental dumping"
need to get rid of it, so it is dumped into poor, developing countries
Are all fuels created equal?
no
Do all reactions give off heat
no
Can we make fossil fuels easily?
not really, it takes a long time
Natural gas
odorless, colorless gas composed primarily of methane (CH4) (0-20% other HCs)
British thermal unit (BTU)
often used to describe the energy content of fuels (1 BTU = 1055 J)
Some natural gas is dissolved in petroleum and can be captured in distillation as "refinery gas", but most comes from
oil or gas wells
Since we are running out of easy oil, we turn to unconventional sources of oil like
oil shale in UT, CO, WY, oil sands in Canada, deep water drilling (oil buried under sea floor)
Where does petroleum (crude oil) come from
oil wells, tarry oil sands and shale
Different types of coal
older coal has less moisture and more carbon, making it a more desirable fuel because it has a higher energy content
Industrial officials on this issue
petcoke has been an important and valuable fuel for decades, and its use recycles a waste product
Typically, aquatic organisms tend to form _________, while terrestrial plants tend to form ____.
petroleum; coal
1 W = 1 J/s translates to
power = energy/time
Reforming
process in which atoms within a molecule are rearranged
Different types of coal have different
properties
